We propose to extend our basic knowledge and theoretical understanding of color vision development with three basic experiments. First, we plan to measure chromatic and luminance contrast thresholds as a function of age. We will follow the development of color vision from its inception at about age 3 months to whenever adult-like color vision is attained. The relative rates of development of chromatic and luminance contrast sensitivity may contribute to our understanding of why the color vision of young infants is so poor. Second, we plan to compare chromatic and luminance contrast sensitivity measured using sinusoidal grating stimuli (the usual stimulus) with chromatic and luminance contrast stimuli measured using edge stimuli, a stimulus that is increasingly being used in vision research. This will help us understand the relation between color vision and spatial vision during development. It is likely that edge stimuli could some day be used in clinical testing of infants, and if so the basic information from this kind of experiment will be important. Third, we plan to measure discrimination thresholds between white and stimuli differing in luminance and/or excitation purity from white. Those thresholds, measured as a function of age, will tell us whether the color vision of infants differs qualitatively from that of adults, or whether it is just uniformly less sensitive. Another set of those thresholds will measure the sensitivity of the individual receptor mechanisms, and, together with the results of the first experiment, will help us arrive at a quantitative understanding of why infants' color vision is poor.